1. Field of the Invention
The invention relates to a radio system for receiving and controlling the reception of broadcast signals, and in particular, a radio system capable of controlling the reception for broadcast signals for use with a vehicle navigation system.
2. Background of the Invention
Nowadays, vehicle navigation systems are often combined with radio systems and form one single head unit used for guiding the driver of a vehicle to a predetermined destination and for functioning as an entertainment system for audio applications. Vehicle radio systems often use reception systems that use multiple antennas for receiving radio signals. When multiple antennas or multiple receivers are used, antenna diversity operating modus or frequency diversity operating modes are also used. Antenna diversity operating system and frequency diversity operating modes are known in the art.
When using antenna diversity operation mode, multiple spatially separated antennas are used to receive radio signals. When the radio system operates in antenna diversity operating mode, the receiver system selects one of the antennas as the source for radio signal processing based on predefined criteria. Such criterion may be, e.g., the received signal strength, interference or noise level, signal-to-noise ratio or other signal quality criteria.
When using frequency diversity operating mode, the radio system includes multiple radio receivers. One of the radio receivers may function as an operating receiver and another receiver may function as a search and check receiver. The operating receiver stays tuned to the frequency of interest to receive and process the received radio signal. Simultaneously, the search and check receiver searches for alternative reception frequencies (AFs) that may provide higher signal quality. If the search and check receiver finds another reception frequency providing higher signal quality, either the operating receiver tunes to the alternate reception frequency or the search and check receiver and the operating receiver switch roles.
Alternatively, antenna phase diversity mode is also known to operate in a system in which a first receiver coupled to a first antenna and a second receiver coupled to a second antenna are tuned to the same frequency. After a phase correction of one of the signals, the two signals are summed to achieve a better signal for further processing the received radio signal. A phase-corrected summation of the signals is described, inter alia, in DE 101 02 616 A1.
Furthermore, modern FM radio transmissions include several types of content. In most cases, the FM radio signal or a particular program is a multiplex signal that includes not only left and right channel audio content, but also data content. The data content may carry program information codes that indicate the name of the audio program, the name of the radio station broadcasting the FM radio signal and/or traffic information. The additional information data, especially traffic information, may be used by the navigation system when calculating a route from the current position to a predetermined destination. Using the traffic information, the navigation may take into account possible traffic congestions or closed routes when calculating the route. When the navigation system calculates a new route, it may need many additional items of information concerning traffic information for the calculated route. The possibility of collecting additional information data depends on the current operating mode of the radio system. In some applications it may be important to receive an optimal radio signal, in other situations it may be helpful to be able to collect as much additional information data as possible, e.g., traffic information.
Normally, one of the standard operating modes of a radio system can be used to achieve a high quality signal. However, when a radio system is operating in a moving vehicle, the operation of a radio system varies frequently due to constant changes in the surround environment. To collect useful data for use by a navigation system, the radio system must be able to not only account for the environmental and situation changes, but also operate in a large variety of modes. Thus, a need exists to provide a radio system having a large variety of operating modes and that is able to adjust operating modes based on different driving situations occurring in a moving vehicle.